Sanyo Electric Co., Ltd.

Sanyo Semiconductor Co., Ltd.

Murata Manufacturing Co., Ltd.

Semiconductor Components Industries, LLC

Tomoaki Nishi

Takashi Noma

Iwao Fukushi

Mitsuru Ooyagi

A light-emitting-element-driving-control circuit comprising: a control circuit to turn on or off a transistor based on an input-control signal, the transistor being connected in series with a light-emitting element and an inductor connected in series and controlling increase and decrease of a driving current of the light-emitting element; a maximum-value-detection circuit to detect a maximum value of the driving current; and a control-signal-generation circuit to generate the control signal for turning on the transistor to increase the driving current at a speed corresponding to a level of a power-supply voltage when the driving current is smaller than the maximum value and turning off the transistor to be kept for a predetermined period to decrease the driving current at a speed corresponding to a level of a forward voltage of the light-emitting element when the driving current reaches the maximum value, based on a detection result of the maximum-value-detection circuit.

Light-emitting element driving control circuit

A main (sub) clock circuit comprising a first (second) capacitor, a first (second) current-supply circuit to supply to the first (second) capacitor a first (third) current for charging at a predetermined-current value or a second (fourth) current for discharging at a predetermined-current value, a first (second) charge/discharge-control circuit to output a first (second) control signal for switching between the first (third) current and second (fourth) current which are supplied to the first (second) capacitor from the first (second) current-supply circuit when a voltage across the first (second) capacitor has reached a first (third) reference voltage or second (fourth) reference voltage higher than the first (third) reference voltage, and a first (second) output circuit to output a main (sub) clock according to the first (second) control signal, the first capacitor having one end connected to a first potential, the second capacitor having one end to which the main clock is input.

Clock generating circuit

A triangle wave generating circuit comprising: a pulse generating circuit configured to generate a plurality of pulse signals with the same period and with phases different from one another; and a plurality of charge/discharge circuits configured to be supplied with the plurality of pulse signals, respectively, the plurality of charge/discharge circuits each including: a current supply circuit configured to supply to a capacitor a first current for charging at a predetermined current value or a second current for discharging at a predetermined current value; and a charge/discharge control circuit configured to switch between the first current and the second current when the pulse signals are supplied thereto and when a voltage across the capacitor reaches a predetermined reference voltage, the first current and the second current supplied from the current supply circuit to the capacitor.

Triangle wave generating circuit

A constant-current circuit comprising: a temperature-compensation circuit to output a temperature-compensated first current; and a current-supply circuit to supply a second current to the temperature-compensation circuit, the temperature-compensation circuit including a voltage-multiplication circuit including a first transistor to generate a base-collector voltage obtained by multiplying a base-emitter voltage by a predetermined ratio, a second transistor identical in conductivity type and substantially equal in base-emitter voltage to the first transistor, a first resistor having two ends connected to a first-transistor collector and second-transistor base, respectively, and a second resistor having two ends connected to first and second-transistor emitters, respectively, the first current being output according to a second-transistor collector current, the second current being supplied to a connection point between a second-transistor base and the first resistor, to generate between both ends of the first resistor a voltage varying substantially in proportion to temperature.

Constant current circuit

The switching control circuit comprises a switching control signal generation circuit that detects a change in ripples of the output voltage and-generates a switching control signal for the on/off control of the switching element to make the output voltage follow the target level; an overcurrent state detection circuit that generates a state signal indicating whether the output current is in an overcurrent state where the output current is equal to or greater than a predetermined current; and a delay circuit that delays the state signal for a same predetermined delay time at both of the times when the output current exceeds the predetermined current and when the output current falls below the predetermined current.

Switching control circuit and self-excited DC-DC converter

A self-excited DC-DC converter includes a switching element that chops an input voltage; a smoothing circuit that smoothes the chopped voltage to generate an output voltage; and a switching control circuit. The switching control circuit includes a switching control signal generation circuit that generates a switching control signal for the on/off control of the switching element by comparing a feedback voltage of the output voltage and a comparison voltage; an output correction circuit that adjusts the comparison voltage according to an error between the feedback voltage and the reference voltage and, when the output current is in the overcurrent state, reduces the level of the comparison voltage; an overcurrent protection signal generation circuit that, when the output current is in an overcurrent state, generates an overcurrent protection signal for turning off the switching element regardless of the switching control signal; and a delay circuit that delays the overcurrent protection signal.

Switching control circuit and self excited DC-DC converter

A self-excited DC-DC converter comprises a switching element that chops a direct-current input voltage; a smoothing circuit that smoothes the chopped voltage to generate a DC output voltage; a switching control signal generation circuit that generates a switching control signal for the on/off control of the switching element by comparing a feedback voltage of the output voltage and a comparison voltage; an output correction circuit that adjusts the comparison voltage according to an error between the feedback voltage and the reference voltage and, when the output current is in the overcurrent state, reduces the level of the comparison voltage; an overcurrent protection signal generation circuit that, when the output current is in an overcurrent state, generates an overcurrent protection signal for turning off the switching element regardless of the switching control signal; and a delay circuit that delays the overcurrent protection signal. Also, a switching control circuit is provided therein.

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Nagaoka, Japan

Tomoaki Nishi